Induction can be used to transfer power wirelessly from a power supply to a mobile phone to be charged. For this purpose the mobile phone can connect to an adapter that can receive the induced power so as to provide a charging current to be fed to the mobile phone. The mobile phone receives the current and feeds it to the connected battery for charging it.
During the charging the adapter can use the inductively received power to inductively send data to the power supply. This data may include information about a status of the charging for example.
However, the impedance of the mobile phone as perceived by the adapter may change during the charging. This may happen due to the mobile phone being used for calling during the charging, for example. Since the adapter and the mobile phone are electrically coupled during charging, thereby forming a single circuit, the impedance changes in the mobile phone are reflected as distortions to the data that is sent to the inductive power supply. The impedance changes may be unpredictable and thereby difficult to compensate for.
Since the mobile phone and the adapter form a single circuit during charging, also noise from the mobile phone can couple with the adapter circuitry and distort the data being induced to the power supply. Furthermore, variations in the distance between the power supply and the adapter may cause distortions in the inductively received data in the power supply, also when charging is not performed.
Accordingly, the data induced to the power supply from the adapter can be distorted in many ways and the status information form the charging can not be obtained in the power supply. Therefore, it may be increasingly difficult for the power supply to determine if the battery is charged and/or to stop charging, or if the adapter is within the range to receive power from the power supply. Consequently, erroneously received data from the adapter may cause the power supply to stop the charging even if the adapter is within the range to receive power or to falsely determine that the adapter is not within the range to receive power.